The invention is generally directed toward weighing refuse collected by a refuse collecting vehicle. The invention is more particularly directed toward statically or dynamically obtaining the accurate weight of refuse loaded by hydraulically driven lifting arms of a refuse collection vehicle. The invention is further focused on the utilization of an hydraulic bypass system for controlling the movement of the arms of an hydraulic lift system of a refuse vehicle through a defined measuring range whereby a microprocessor converts electrical analog input signals from a transducer and digitally converts the input to serially total tare weights over time.
The immediate concerns of society include the need for effectively treating and disposing refuse of all kinds, including solid municipal waste, particularly for landfill burial. Refuse haulers are usually contracted to collect refuse containers from commercial, factory and other business sites on a regular basis. When the containers are due for collection, the refuse vehicle engages the container and dumps it into a receptacle that is part of the vehicle. In order for scavenger or waste hauling companies to dump loads at landfills, a per ton charge is typically assessed. While in the more crowded areas of the country, charges at the rate of $130.00 per ton are not uncommon, they usually fall in the range of about $30.00 to about $40.00 per ton. These charges and others are borne by the customer and the waster hauler will add an incremental amount more as profit. Therefore it is critical to both the customer and the hauler to know what amount is charged for the refuse and waste landfill fees.
It is difficult to estimate costs when different amounts might be collected from a customer on an ongoing basis. The volume and weight of refuse discarded may vary from week to week in a wide range, particularly for industrial plants where waste might vary from metal or wood to light plastics. Also, in bidding on jobs, a waste hauler might estimate too high or low. Estimating purely on the basis of volume is illogical because the charges for dumping at a landfill are made on a per ton basis. Thus the customer might be paying too much or too little depending upon its particular business and how the waste hauler sets its charges. These problems have been variously addressed in the prior art and proposed solutions usually involve weighing a container picked up by refuse vehicle when it is full and then when it is empty.
Typical refuse collection vehicles are usually of the type that have either a front loading or a rear loading set of hydraulic arms that are joined to extending engagement arms for engagement with engageable sleeve-like portions of the containers. The pivotal lifting arms are usually in the shape of a large downward yoke or U-shape and two such arms typically pivotally straddle the front of the cab or the rear of the refuse vehicle.
Hydraulic lift cylinders may either pull or push the arms during lifting depending upon the mechanism. The engagement arms are aligned with the engageable portions of the container and the refuse vehicle operator positions the vehicle while at the same time working the hydraulic system to engage the container. Then, the lift arms are drivingly pivoted and the container is lifted and leveled as it travels upwardly to be ultimately dumped into the receptacle of the vehicle.
Typical weighing procedures involve the use of load cells or transducers providing analog electrical signals proportionate to the loading sensed. The signals are converted by an analog/digital converter and may be tabulated and stored by a microprocessor.
The utilization of transducers in the form of load cells is shown in U.S. Pat. No. 4,714,122 wherein the transducer is mounted on the lifting element of a refuse truck. The signal is generated when the container is at a certain point relative to the truck body by virtue of a sensing switch activated by a cam surface on the lifting arms. However, load cells have been found to be unreliable and are easily damaged. The dynamics in lifting heavy weights creates significant vibration, stuttering and unsteadiness as the lift arms in the powerful hydraulic systems of a refuse vehicle are operated. Waiting for vibration and shaking to stop in order to make an accurate weighing wastes costly minutes, even for static measurements. Accuracy is naturally more difficult should dynamic weighing be attempted as the load is in motion.
Another use of load cells as found in U.S. Pat. No. 4,645,018, wherein the gross weight and the empty weight of the container are determined while the container is being emptied. A strain gauge (load cell) sets in a sliding body that is arranged with the lifting arms so that the sliding body will transmit the value of the weight of the refuse container to the load cell while it is displaced downwardly. The locking device is to be released and the dead weight of the container is measured by the load cell at the empty position. The signals for the individual full and empty weights are electrically communicated to a data recording unit.
Other related hydraulically operated machines have been required to accurately measure various materials to be loaded and carried, such as in U.S. Pat. No. 2,851,171 directed towards a material handling vehicle with a pivotable front loading bucket. An hydraulic pressure responsive gauge is provided in the hydraulic system of this device and is calibrated in units of weight. In that device the gauge is connected in an hydraulic series circuit with an hydraulic pressure snubber and gauged control valve. The gauge being in the hydraulic series with the lifting cylinder for the bucket. An analog-to-digital conversion employing a transducer, or the like, is not provided. A pressure gauge is difficult to keep calibrated and often is subjected to damage and inaccuracy during changeable weather conditions. The operation of this prior art system creates vibration and instantaneous hydraulic pressure surges so that a snubber is provided to dampen the effect, but requires a long time period to effectively dampen and is not highly accurate. Such devices do not teach utilization in an hydraulic system accommodating a microprocessor for tabulating over time the tare weights of a series of loads.
Systems for lowering loads onto a scale are known, such as in U.S. Pat. No. 3,612,490 where a skip loader is lowered by means of controlling the flow of hydraulic fluid from the lower end of an hydraulic cylinder while the loader is being lowered onto the weigh scale. An accurate measurement of loading in an hydraulic refuse container lifting system is not provided and weighing in this patent is independent of any hydraulic pressures.
A weighing system that provides for both dynamic and static weighing that controls the ascent and descent of lifting arms, or container-engageable lifting means, is not shown or suggested by the previous weighing systems.
It is accordingly a primary goal of this invention to provide for the accurate weighing of full and empty refuse containers by eliminating the vibration, pressure fluctuations, pressure surges and random shaking encountered in lifting heavy waste and refuse container loads.
It is another important goal of the invention to provide for a controlled weighing step in the lifting and dumping of a refuse container whereby sensed gross and empty weight values may be electrically signalled to a microprocessor wherein the tare weight may be calculated and serially tabulated during the course of the daily operation of a refuse vehicle.
It is another important objective of the invention to eliminate the problems with load cells and strain gauges previously used at the mechanical arms of refuse lifting devices and instead implement a separate hydraulic bypass system to the main hydraulic system, which is fluidly associated with the lifting circuit of the main system, whereby accurate calibrated readings may be made.
It is a further goal of the invention to provide for a controlling hydraulic bypass circuit that permits both manual and automatic weighing in conjunction with an analog/digital converting and microprocessing system.
It is yet another critical goal of the invention to provide a system for controlling the movement of a lift arm whereby accurate weights may be sensed by a transducer during both static or dynamic weighing modes, depending on the software program used, whereby to be usable with microprocessors having either or both capabilities.
It is an allied goal of the invention to overcome the imprecision found in dynamic weighing systems in the prior art by means of making possible the accurate calibration of a transducer by virtue of controlling over a limited path of motion the ascent or descent of the lifting arm assembly of a refuse collection vehicle.
It is yet another object of the invention to implement a transducer in a bypass hydraulic circuit which may be calibrated for different weight ranges, and types of refuse containers, in conjunction with a microprocessor that has numerous scales for the different ranges.
It is concomitantly a critical goal to provide for a weighing system that is reliable during the course of daily loadings and of dumping containers into a refuse vehicle, which involves severe dynamic impacts, variable loading, extreme weather conditions and human error in positioning the container.
It is an ultimate goal of the invention to provide for a weighing system that may be usable by lift cylinders that operate lift arms either by pushing or pulling them to pivot the lift arms during collection.